Silver halide photographic emulsion

ABSTRACT

A silver halide photographic emulsion characterized in that it comprises silver halide grains which are reduction-sensitized during the process of growing said grains and containing a compound of the formula ##STR1## wherein R 1  and R 2  are selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, an acyl group and a cycloalkyl group and R 3 , R 4 , R 5  and R 6  are selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxy group, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an alkoxy group, an acyl group, a carboxyl group, an aldehyde group, an amino group, a sulfo group, an alkylthio group, an acylamino group, an aryloxy group, an arylthio group, an alkylamino group, an alkoxycabonyl group and a sulfonamide group. The emulsion exhibits both high sensitivity and improved stability as compared with prior art compositions.

The present invention relates to the silver halide emulsion having highsensitivity and excellent preservability.

In recent years, a highly sensitive silver halide photographic materialhas been required. For example, as for films for amateur use a highshutter speed has been required for the purpose of eliminating a pictureblur resulted from miniaturizing a film frame size, and as to color andblack-and-white photoprinting papers a rapid processing is required, andas to photosensitive materials for the graphic arts use a highsensitivity is required from the view points of the adoption ofelectronics and the simplification in a printing process, also as toX-ray photosensitive materials the reduction of radiation dose isstrongly requested.

Quite recently, it is emphatically required to save silver becausesilver price has been sharply raised. To satisfy this requirement it isindispensable to establish a technology for increasing the sensitivity.

As for the technology for increasing the sensitivity, there have so farbeen known the chemical sensitizing in the individual use or for a jointthereof, for example, sulfur sensitizing, noble metal sensitizing suchas gold, palladium, platinum and iridium sensitizing, seleniumsensitizing and reduction sensitizing.

Among the above chemical sensitization, reduction sensitization has beenwell known as described in Japanese Patent Publication Open to PublicInspection No. 87825/1973 for example, that this sensitization can beone of the most promising chemical sensitizing technologies, if this isused jointly with gold and/or sulfur sensitization.

However, it has also been known that the silver halide photosensitiveemulsions which were highly sensitized by the reduction sensitizationhave the serious defects that the photographic materials will result indesensitization and soft gradation during the preservation. It has beenconsidered that the above-mentioned defects are caused from the factthat the said silver halide photosensitive emulsions are thermallyunstable because the sensitized nuclei produced by reduction sensitizingare the fine silver nuclei in which several silver atoms were coheredtogether.

Among persons skilled in the art, it has been well known the facts thatthe said reduction sensitization is inferior in itself in preservabilityin spite of its high sensitivity and that the preservability thereofcannot be fitted for the practical use.

Accordingly, it is an object of the invention is to provide a silverhalide photosensitive emulsion having a high sensitivity and an improvedpreservability and a producing method thereof.

It is another object of the invention is to provide a means forimproving the preservability of a silver halide photosensitive emulsionhighly sensitized by reduction sensitizing.

Other and further objects of the invention will appear from thedescription of the present specification.

The object of the present invention may be achieved by a silver halidephotographic emulsion comprising silver halide grainsreduction-sensitized in a process of growing the silver halide grainsand the compound represented by the following general formula [I],##STR2## (wherein R₁ and R₂ are selected from the group consisting of ahydrogen atom, an alkyl group, an alkenyl group, an aryl group, an acylgroup and a cycloalkyl group and R₃, R₄, R₅ and R₆ are selected from thegroup consisting of a hydrogen atom, a halogen atom, a hydroxy group, analkyl group, an alkenyl group, a cycloalkyl group, an aryl group, analkoxy group, an acyl group, a carboxyl group, an aldehyde group, anamino group, a sulfo group, an alkylthio group, an acylamino group, anaryloxy group, an arylthio group, an alkylamino group, an alkoxycarbonylgroup and a sulfoamide group.)

These groups may be substituted by group such as halogen atom, hydroxygroup, carboxy group, sulfo group, cyano group, alkyl group, alkenylgroup, alkoxy group, alkylthio group, alkenyloxy group, alkenylthiogroup, aryl group, arylthio group, arylamino group, alkylamino group,alkenylamino group, acyl group, acyloxy group, acylamino group,carbamoyl group, sulfonamide group, sulfamoyl group, alkoxycarbonylgroup and aryloxycarbonyl group.

Alkyl groups represented by the characters, R₁ -R₆ in General Formula[I] may be of either the straight chained or the branch-chained,preferably be the one having 1-32 carbon atoms, for example, methyl,ethyl, n-butyl, 1-butyl, 3,5,5,-trimethyl hexyl, n-octyl, and n-dodecylare given.

Alkenyl groups represented by R₁ -R₆ may be of either thestraight-chained or the branch-chained, preferably be the ones having1-32 carbon atoms, for example, alkyl, butynyl, octenyl and olenyl aregiven. As for aryl group represented by R₁ -R₆, phenyl and naphthyl aregiven. Similarly, as for acyl group, acetyl, butanoyl, dodecanoyl,benzoyl and cinnamoyl are given. As for cycloalkyl group, the one having5-7 members is preferable, for example, cyclopentyl and cyclohexyl aregiven, respectively.

As for halogen atom represented by R₃ -R₆, fluorine, chlorine, bromineand iodine are given as the example. As for alkoxy group, methoxy,ethoxy and t-butoxy are given. As for alkylthio group, methylthio andn-dodecylthio are given. As for aryloxy groups, phenoxy and naphthoxyare given. As for arylthio group, phenylthio is given. As for acylaminogroup, acetylamino, octanoylamino and benzoylamino are given. As foralkylamino group, methylamino, diethylamino and isopropylamino aregiven. As for alkoxycarbonyl group, methoxycarbonyl and ethoxycarbonylare given. As for sulfonamide groups, methyl sulfonamide and phenylsulfonamide are given, respectively.

The following example shown in Table 1 are exemplary of the chemicalcompound of the invention formulated in General Formula [I]; howeverthese examples are not to be construed to limit the scope of theinvention.

    TABLE-1      Compound example:      ##STR3##      No. R.sub.1 R.sub.2 R.sub.3 R.sub.4 R.sub.5 R.sub.6      1 H H H H H H 2 H H CH.sub.3 H H H 3 H H C.sub.2 H.sub.5 H H H 4 H H     OCH.sub.3 H H H 5 H H OC.sub.2 H.sub.5 H H H 6 H H COOH H H H 7 H H     COOCH.sub.3 H H H 8 H H COCH.sub.3 H H H 9 H H CH.sub.2CHCH.sub.2 H H  H     10 H H C.sub.15 H.sub.31 H H H      11 H H     ##STR4##      H H H      12 H H     ##STR5##      H H H  13 H H CONH.sub.2 H H H 14 H H Cl H H H 15 H H CH.sub.2 COOH H H H      16 H H     ##STR6##      H H H  17 H H CH.sub.2 OH H H H 18 H H H CH.sub.3 H H 19 H H H NH.sub.2 H      H 20 H H H C(CH.sub.3).sub.3 (t) H H      21 H H H     ##STR7##      H H  22 H H  H SO.sub.3 H H H 23 H H H Br H H      24 H H H     ##STR8##      H H      25 H H H     ##STR9##      H H      26 H H H     ##STR10##      H H      27 H H H     ##STR11##      H H  28 H H H CHO H H 29 H H H (CH.sub.2).sub.3 CH.sub.3 H H 30 H H     CH.sub.3 CH.sub.3 H H 31 H H OH CH.sub.2COCH.sub.3 H H 32 H H CH.sub.3 H C     H.sub.3 H 33 H H  Br H CH.sub.3 H 34 H H OH H COOH H 35 H H OCH.sub.3 H     COCH.sub.3 H 36 H H OH H OH H 37 H H OCH.sub.3 H Cl H  38 H H OH H      ##STR12##      H  39 H H C(CH.sub.3).sub.3 (t) H CH.sub.3 H  40 H H CH.sub.3 H      ##STR13##      H      41 H H OCH.sub.3 H H     ##STR14##      42 H H CH.sub.3 H H     ##STR15##       43 H H OH H H NH.sub.2 44 H H OH H  H OH 45 H H H Br COOH H 46 H H H     CH.sub.3 CH.sub.3 H 47 H H H CH.sub.3 C(CH.sub.3).sub.3 (t) H 48 H H     CH.sub.3 OH H CH(CH.sub.3).sub.2 49 H H OH OH H OH 50 H H OH NH.sub.2 H     NH.sub.2 51 H H OCH.sub.3 OCH.sub.3 H CH.sub.3  52 H H OH COCH.sub.3 H      ##STR16##       53 CH.sub.3 CH.sub.3 H H H H 54 CH.sub.3 H H H H H 55 CH.sub.3 H H Cl     H Cl 56 H H CH.sub.3 OH OCH.sub.3 OCH.sub.3  57 H H OH Cl CH.sub.3      ##STR17##       58 CH.sub.3 CH.sub.3 H Br COOH H 59 CH.sub.3 CH.sub.3 H H H CH.sub.2     CH.sub.2 COOH 60 C.sub.2 H.sub.5 H H H H CHO 61 CH.sub.3 H H CH.sub.2     CH.sub.2 NH.sub.2 OH H      62     ##STR18##      ##STR19##      H      ##STR20##      H H      63     ##STR21##      H H H NH.sub.2 H 64 COCH.sub.3 COCH.sub.3 C(CH.sub.3).sub.3 (t) H     C(CH.sub.3).sub.3 (t) H 65 C.sub.2 H.sub.5 H H H CHCHCH.sub. 3 H  66 H H C     OOC.sub.2      H.sub.5     ##STR22##      ##STR23##      ##STR24##       67 C.sub.2 H.sub.5 H CH.sub.3 H C(CH.sub.3).sub.3 (t) H 68 CH.sub.2     CHCH.sub.2 H H H H H      69     ##STR25##      H H H H H      70     ##STR26##      H H H H H      71 H H OCH.sub.3 H H     ##STR27##       72 H H OCH.sub.3 H H SO.sub.2      NH.sub.2 73 H H OCH.sub.3 H H SCH.sub.3

The above compounds can easily be synthesized through such a process asdescribed in Eugen Muller, "Methoden der Organischer Chemie," 4th ed.,Georg Thieme, 1976, Bd. 6/Ic, and can also be procured on the regularmarket.

Herein, the expression, "reduction-sensitized in a process of growingthe silver halide grains" means not only that silver halide grains arereduction-sensitized in the state where they are being grown in amanufacturing process, but also that they are reduction-sensitized inthe state where they are not grown, but the grains having already beenreduction-sensitized are grown thereafter in a manufacturing process. Inother words, it is to be understood that that silver halide grainsreduction-sensitized in a process of growing the silver halide grainscontain the silver halide grains which have been prepared through themanufacturing process including the process wherein reduction-sensitizedsilver halide grains are grown.

The reduction sensitization in a process of growing the silver halidegrains abovementioned produces a silver nuclei in the interior of asilver halide grain. This silver nuclei is capable of scavenging apositive hole generated by light absorption.

The reduction sensitization of the invention are preferred by addingreducing agent and/or water-soluble silver salt into silver halideemulsion so that the silver halide grains in silver halide emulsion canbe reduction-sensitized in a process of their growing.

As for the preferable reducing agents, thiourea dioxide and stannouschloride are given, and it is suitable to use the former, or the latter,at the ratio of approx. 0.01 mg-approx. 2 mg, or approx. 0.01 mg-approx.3 mg respectively per mol of silver halide. Other suitable reducingagents include polyamines such as hydrazine and diethylene triamine, andsulfites.

As for water-soluble silver salts, silver nitrate is preferable and theso-called silver ripening, which is included in reduction sensitization,is performed by adding water-soluble silver salt. The suitable value ofpAg in silver ripening is 1-6, particularly 2-4 (herein, the value ofpAg is a common logarithm of the reciprocal of Ag⁺ concentration.)

As for the conditions of reduction sensitization, the preferable scopesare approx. 30° C.-80° C. for temperature, approx. 10 min-200 min. fortime, approx. 5-11 for pH and approx. 1-10 for pAg.

At any arbitrary time before, during or after the said reductionsensitization, an emulsion may be added with the following chemicalsensitizers; sulfur sensitizers such as sodium thiosulfate and thiourea;noble metal sensitizers such as gold sensitizers of which chloroaurateand gold trichloride are given in the concrete, and palladiumsensitizers of which palladium chloride and chloropalladiate are givenin the concrete, platinum compounds and iridium compounds; and seleniumsensitizers such as selenious acid and selenourea; and one or more kindsof these sensitizers may be added in an emulsion.

From the viewpoint of obtaining high sensitivity, it is preferable thatthe reduction-sensitized emulsions of the invention are to be gold-and/or sulfur-sensitized after the completion of desalting process.

Reduction sensitization is also possible after the completion of theabove mentioned gold- and/or sulfur-sensitization.

The compounds formulated by General Formula [I] of the invention(hereinafter referred to as the compound of the invention) are to becontained in silver halide photographic emulsion containing thereduction sensitized silver halide grains of the invention, and as forthe containing processes, it can be done through either the process inwhich the compounds of the invention are to be contained directly intothe said emulsion or the process in which the said compounds are to beadded in a composite for coating use such as a layer (e.g., a protectivelayer, irradiation prevention layer, filter layer or other interlayers)adjoining said emulsion layer in a photosensitive material and then tobe contained in said emulsion (that is the emulsion layer) through acoating process or by diffusion to be made thereafter.

For the purpose of containing the compounds of the invention into theaforementioned constituent layer of a silver halide photosensitivematerial, it is advantageous to add the compounds of the invention inform of solution into the coating composites for the said constituentlayer use. As for the solvents to be used for this purpose, there aregiven a variety of solvents, among those of which aqueous or hydrateorganic solvents not having a bad influence upon silver halide emulsionsor others are preferable, for instance, methanol, ethanol, isopropylalcohol, alcohol fluoride, ethylene glycol monomethyl ether, dimethylformaldehyde and acetonitrile, and the compounds of the invention may bedissolved in the single or mixed solvent as above given.

In the case of adding the compounds of the invention into silver halideemulsions, the timing of adding thereof depends upon the kinds andpurposes of a photosensitive materials having a photosensitive layercoated with the said silver halide emulsions, however it will doessentially to add the said compounds of the invention at any time andstage for preparing a silver halide emulsion, nevertheless, it is notpreferable to add the said compounds before the desalting because thecompounds are eluted by the desalting but preferable to add after thesecondary ripening was completed.

As for the timing for adding the said compounds into a coating compositefor a constituent layer use contained with silver halide emulsions, thetiming just prior to the coating is more preferable.

The amount added of the compound of the invention varies according tothe kinds of silver halide to be used in a silver halide photographicemulsion, the grain diameters or crystal habits of silver halide, thepresence of other additives for photographic use such as stabilizers andsensitizing coloring-matters, temperatures for processing said silverhalide photographic emulsion, or compositions of a processing solution.However the amount added of the compounds is generally 1 mg-10 g per molof silver halide, preferably 10 mg-2 g.

In the case of adding the compound of the invention in silver halideemulsion, an excellent preservability can be obtained by adding eitheronly one kind of said compound or more than two kinds of them.

Also, it can do without any trouble to make the compounds of theinvention coexist at the same time in silver halide photographicemulsion with other additives to be added for the purpose of preventingfrom producing fogs and lowering the sensitivity in the preparingprocess, preservation period and the processing steps of silver halidephotographic emulsions. As for the said other compounds, any of theadditive publicly well-known in persons skilled in the art can be usedincluding the famous compounds such as4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene, 5-mercapto-1-phenyltetrazole, and 2-mercaptobenzothiazole.

The working effects of the invention cannot be obtained until thecompounds of the invention are combinedly used with silver halide grainsto be used in the invention, however it is impossible to obtain thesimilar effects even if used a compound of which structure is similar tothe ones of the invention, such as hydroquinone compound or resorcinolcompound.

The silver halide grains to be used in the invention can be prepared byapplying the process such as neutral processes as described in theliterature such as T. H. James, "The Theory of the Photographic Process"4th ed., Macmillan, 1977, pp. 88-104, acid processes, ammonia processes,regular order mixing, inverse order mixing, double-jetting processes,controlled-double jetting processes, conversion processes, andcore/shell processes. As for the compositions of silver halide, anyoneof silver chloride, silver bromide, silver chlorobromide, silveriodobromide, silver chloroiodobromide and so on can be used.

There is no particular limitation of silver halide grains in the sizes,distribution, crystal habits, forms (e.g., regular crystal form andtwinned crystal form), etc., however the grains having the comparativelyuniform diameters of 0.1-2μ are preferable. And in these silver halidegrain or in silver halide emulsion, iridium salts and/or rhodium saltsmay also be contained therein for improving the flash-exposurecharacteristics thereof.

Further, they can be optically sensitized in the desired wave-lengthrange as occasion demands by making use of optical sensitizers such ascyanine and merocyanine sensitizing dyes independently or jointly.

For example the sensitizing dyes described in the following U.S. Patentscan be used; U.S. Pat. Nos. 2,493,784, 2,519,001, 2,977,229, 2,480,343,3,672,897, 3,703,377, 2,688,545, 2,912,329, 3,397,060, 3,511,664,3,522,052, 3,527,641, 3,615,613, 3,615,632, 3,615,635, 3,615,641,3,617,295, 3,617,293, 3,628,964, 3,635,721, 3,656,959, 3,694,217,3,743,510, 3,769,301, 3,793,020.

As for the vehicles for silver halide photographic emulsions of theinvention, gelatin, gelatin derivatives, synthesized hydrophilicpolymers can be used and a variety of the additives for photographic usecan also be contained therein.

As for the hardening agents, aldehyde compounds, ketone compounds,halogen substituted acids such as mucochloric acid, ethylene iminecompounds, vinyl sulfonic compounds, etc. can be used. As for thespreading agents, saponin, lauryl or oleyl monoether, etc. are used.

As for the development accelerating agents, there is no particularlimitation and the compounds such as benzimidazole (for example, the onedescribed in Japanese Patent Open to Public Inspection No. 24427/1974)and quaternary ammonium salts can be used.

As for the physical property improving agents, there can be containedwith polymer latexes comprising homo- or copolymers such asalkylacrylate, alkylmethacrylate and acrylic acids.

And the silver halide photographic emulsions relating to the inventioncan be added with an antistatic agent such as the compounds obtained byaddition-copolymerizing glycidol and ethylene oxide with phenol aldehydecondensation products (e.g., the antistatic agents described in JapanesePatent Open to Public Inspection No. 56220/1976), lanolin ethylene oxideaddition products and alkaline metal salts and/or alkaline earth metalsalts (e.g., Japanese Patent Application No. 145022/1978), water-solubleinorganic chlorides and matting agents (Japanese Patent Open to PublicInspection No. 161230/1980), addition condensation products obtained byaddition-condensing glycidol and ethylene oxide with phenol aldehydecondensation products, and fluorine containing succinic acid compounds(e.g., Japanese Patent Open to Public Inspection No. 48520/1979).

Further, pH adjusting agent, thickening agent, graininess improvingagent, matting agent, etc. can be contained therein. Besides, it is notpreferable to contain a strong oxidizing agent in the photographicemulsions of the invention.

In the case that the photographic emulsions of the invention are appliedto a silver halide color photographic sensitive material, no defect iscaused at all even if the photographic emulsion of the invention is madeco-exist with anyone of a variety of constituent factors of saidphotosensitive materials which are others than the various additivesgiven above and well-known by the engineers skilled in the art. As forthe examples of the constituent factors falling under the categorythereof, there are given the compounds, wherein coloring matters areproduced by reacting with an oxidized developing agent, that is, theso-called antidiffusion type couplers. More in detail, yellow couplerswhich are typified by diketomethyl couplers, magenta couplers typifiedby 5-pyrazolone couplers, and cyan couplers typified by phenol ornaphthol couplers, and besides, there are alos given the so-called DIRcouplers which discharge a developing inhibitor on a coloring reaction,and the so-called colored couplers which adjust a masking-density. Therehave been exemplified in "Research Disclosure" (R.D.) 9232.

As for the kinds of silver halide photographic sensitive materials towhich the photographic emulsions of the invention are applicable, anyoneof color printing papers, color negative films, color positive films orblack-and-white films (e.g., photosensitive material for X-ray use orfor printing use), diffusion transfer type photosensitive materials, orthe like, will do.

A photo-exposure of the photographic emulsions relating to the inventiondepends upon the states of an optical sensitization, the purposes ofusing the said emulsion, however a variety of light sources can be usedsuch as tungsten, fluorescent lamp, mercury lamp, arc lamp, xenon,sunlight, xenon flash, cathode-ray tube flying spot, laser beam,electron beam, X-ray, fluorescent screen for radiographic use and thelike, can suitably be used, and the exposure time is normally at 1/10³-100 seconds and besides, with a xenon flash, cathode-ray tube, or laserbeam, a rapid exposure to light of 1/10⁴ -1/10⁹ sec. can be applied touse.

Next, the more concrete description of the invention will be madereferring to the examples, however it is to be understood that thepresent invention shall not be limited thereto.

EXAMPLE 1

Silver iodobromide emulsion containing 1.5 mol of silver iodide wasprepared with being controlled at 60° C., pAg=8 and pH=2.0, through adouble-jet process, and thus the monodispersed cubic emulsion having anaverage grain diameter of 0.5μ was obtained. Thus obtained emulsion wasdevided by two portions after desalted. One of the devided portion wasadded with silver nitrate solution and silver-ripened at 50° C., pAg=3,and pH=6, that was designated as Emulsion No. 1, and the other portionwas not silver-ripened, that was designated as Emulsion No. 2.

Each of the emulsions was further added with silver nitrate solution andthe solution containing potassium bromide and potassium iodide through adouble-jet process and thus the grain of each emulsion was grown from0.5μ up to 1.2μ in diameter. After desalted these two kinds of grainshaving the diameter of 1.2μ were gold-sensitized and fulfur-sensitived,and then Emulsion No. 2 only was further devided by two portion, and oneof the portions was added with silver nitrate solution andsilver-ripened at 50° C., pAg=4.5 and pH=6 and added further withpotassium bromide solution. Thus obtained emulsion was designated asEmulsion No. 3. The above three kinds of emulsion were respectivelyadded with 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene, and devided andadded with the compounds in the devided emulsion respectively.

The normal additives for photographic use such as spreading agent,thickening agent and hardening agent were added into these emulsionsrespectively. And then the emulsions obtained were respectively coatedon a polyethylene terephthalate film base and dried up so that theamount of silver can become at the ratio of 50 mg/100 cm², through aconventional process, and thus Samples No. 1-12 were prepared.

Sensitometry of the each sample was performed as follows. The lightsource of the color temperature at 5400° K. was used for exposure withwhich exposure was made for the period of 1/50 sec. through an opticalwedge. The amount of exposure to light was 3,2 C.M.S. Development wasperformed at 35° C. for 30 sec. by making use of the followingDeveloper-1:

Developer-1

Sodium sulfite anhydrous: 70 g

Hydroquinone: 10 g

Boric acid anhydrous: 1 g

Sodium carbonate monohydrate: 20 g

1-phenyl-2-pyrazolidone: 0.35 g

Sodium hydroxide: 5 g

5-methyl-benzotriazole: 0.05 g

Potassium bromide: 5 g

Glularaldehyde hydrogensulfite: 15 g

Glacial acetic acid: 8 g

Add water to make: 1 ltr.

Sensitometric tests were performed with both samples immediately aftercoated and the samples heat-treated at 50° C. and 80% R.H. and for theperiod of 72 hours, respectively.

The results obtained are shown in Table-1. Sensitivities thereof areexpressed in the values relative to that of Sample No. 1 immediatelyafter coated taking the value of 100. In the table, the character, S,represents a sensitivity. Fog represents a fog density and γ representsa contrast grade.

                                      TABLE-1                                     __________________________________________________________________________             Silver                                                                             Silver                                                                   ripening                                                                           ripening        Developed                                                                             Developed                                        inside                                                                             on the          immediately                                                                           after heat-                             Sample                                                                            Emulsion                                                                           the  grain                                                                              Compound added                                                                           after coated                                                                          treated                                 No. No.  grains                                                                             surface                                                                            (mg/AgX mol)                                                                             S  Fog                                                                              γ                                                                         S Fog                                                                              γ                            __________________________________________________________________________    1   1    Yes  No   None       100                                                                              0.05                                                                             2.3                                                                             65                                                                              0.03                                                                             2.2                                2   "    "    "    Compound 1                                                                           300mg                                                                             100                                                                              0.04                                                                             2.3                                                                             95                                                                              0.03                                                                             2.2                                3   "    "    "    Compound 2                                                                           300mg                                                                             100                                                                              0.04                                                                             2.3                                                                             97                                                                              0.03                                                                             2.3                                4   "    "    "    Control                                                                              300mg                                                                             95 0.04                                                                             2.3                                                                             60                                                                              0.03                                                                             2.2                                                   compound A                                                 5   2    No   "    None       75 0.05                                                                             2.2                                                                             45                                                                              0.03                                                                             2.1                                6   "    "    "    Compound 1                                                                           300mg                                                                             75 0.04                                                                             2.2                                                                             45                                                                              0.03                                                                             2.1                                7   "    "    "    Compound 2                                                                           300mg                                                                             75 0.04                                                                             2.2                                                                             45                                                                              0.03                                                                             2.2                                8   "    "    "    Control                                                                              300mg                                                                             70 0.04                                                                             2.2                                                                             40                                                                              0.03                                                                             2.0                                                   Compound A                                                 9   3    "    Yes  None       92 0.06                                                                             2.2                                                                             55                                                                              0.09                                                                             2.0                                10  "    "    "    Compound 1                                                                           300mg                                                                             90 0.05                                                                             2.2                                                                             58                                                                              0.05                                                                             2.1                                11  "    "    "    Compound 2                                                                           300mg                                                                             90 0.05                                                                             2.2                                                                             57                                                                              0.05                                                                             2.1                                12  "    "    "    Control                                                                              300mg                                                                             88 0.05                                                                             2.2                                                                             53                                                                              0.06                                                                             2.0                                                   Compound A                                                 __________________________________________________________________________     Note:                                                                         ##STR28##                                                                

As is obvious from Table-1, a photographic emulsion of which thesensitivity and preservability have both been greatly improved can beobtained by containing the compound of the invention in silver halideemulsion in which reduction-sensitization was processed inside thesilver halide grains thereof. In contrast with the above, such effectsas above cannot be obtained from the samples in which thereduction-sensitization was processed on the silver halide grainsurfaces or with the samples in which a compound other than but similarto those of the invention was used.

There has been obtained the similar results from the same experiment asperformed in this example, except that silver ripening was replaced bythiourea dioxide.

EXAMPLE-2

In Emulsion No. 1 and No. 3 of Example-1, Compound No. 1 and No. 2thereof were replaced by Compound No. 4, No. 14 and No. 20 and theemulsions thus prepared were coated on and then dried up, and thusSample No. 13-No. 22 were obtained. Then, these samples were exposed tolight and developed together with Sample No. 1 and No. 9 of Example-1through the process similar to that taken in Example-1, and thepreservability of each sample, in the capability for a photographicmaterial, was tested.

The results obtained are shown in Table-2. Sensitivities thereof areexpressed in the value relative to that of Sample No. 1 just aftercoated taking the value of 100.

                                      TABLE-2                                     __________________________________________________________________________                            Developed                                                                             Developed                                         Emul-                                                                             Silver          just after                                                                            after heat-                                   Sample                                                                            sion                                                                              ripen-                                                                            Compound added                                                                            coated  treated                                       No. No. ing (mg/Ag mol) S  Fog                                                                              γ                                                                         S  Fog                                                                              γ                                 __________________________________________________________________________    1   1   Inside                                                                            None        100                                                                              0.05                                                                             2.3                                                                             65 0.03                                                                             2.2                                             of                                                                            grain                                                                 13  "   Inside                                                                            Compound 4                                                                           200mg                                                                              100                                                                              0.04                                                                             2.3                                                                             93 0.03                                                                             2.3                                             of                                                                            grain                                                                 14  "   Inside                                                                            "      500mg                                                                              98 0.04                                                                             2.4                                                                             97 0.03                                                                             2.3                                             of                                                                            grain                                                                 15  "   Inside                                                                            "      1000mg                                                                             96 0.03                                                                             2.5                                                                             100                                                                              0.02                                                                             2.4                                             of                                                                            grain                                                                 16  "   Inside                                                                            Compound 14                                                                          200mg                                                                              100                                                                              0.04                                                                             2.3                                                                             92 0.03                                                                             2.3                                             of                                                                            grain                                                                 17  "   Inside                                                                            "      500mg                                                                              99 0.04                                                                             2.4                                                                             97 0.03                                                                             2.3                                             of                                                                            grain                                                                 18  "   Inside                                                                            Compound 20                                                                          200mg                                                                              100                                                                              0.04                                                                             2.3                                                                             93 0.03                                                                             2.3                                             of                                                                            grain                                                                 19  "   Inside                                                                            "      500mg                                                                              98 0.04                                                                             2.4                                                                             96 0.03                                                                             2.3                                             of                                                                            grain                                                                 9   3   Grain                                                                             None        92 0.06                                                                             2.2                                                                             55 0.09                                                                             2.0                                             sur-                                                                          face                                                                  20  "   Grain                                                                             Compound 4                                                                           500mg                                                                              89 0.05                                                                             2.2                                                                             57 0.05                                                                             2.1                                             sur-                                                                          face                                                                  21  "   Grain                                                                             Compound 14                                                                          "    90 0.05                                                                             2.1                                                                             58 0.05                                                                             2.1                                             sur-                                                                          face                                                                  22  "   Grain                                                                             Compound 20                                                                          "    90 0.05                                                                             2.2                                                                             57 0.05                                                                             2.0                                             sur-                                                                          face                                                                  __________________________________________________________________________

As is obvious from Table-2, there can be obtained a photographicemulsion of which the sensitivity is high and the preservability isgreatly improved by making use of the compounds of the invention forsilver halide emulsion in which reduction-sensitization was processedinside the silver halide grains thereof. On the other hand, such effectsas above cannot be obtained with silver halide emulsion in whichreduction-sensitization was processed.

There has been obrained the similar results from the same experiment asperformed in this example, except that silver ripening was replaced bythiourea dioxide.

EXAMPLE-3

The preparation was performed similarly to that for Emulsion No. 1 ofExample-1 up to the step of adding 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene therein.

Further a series of popular additives for photographic use such asspreading agent, thickening agent and hardening agent were addedtherein, and the coating and drying were then made in the conventionalprocess so that the Ag amount thereof can be at the ratio of 50 mg/cm²on sublayered polyethylene terephthalate film base together with aprotective layer. At that time, the protective layer was devided byseven portions and one of them was used for the control and the othersix of them were added with the compounds indicated in Table-3,respectively to prepare the samples.

Among these samples thus prepared, the samples just after coated and theother samples heat-treated at 55° C. and 80% R.H. and for the period of27 hours, have respectively been exposed to light and then developed,and thus tested the preservability in the capability for a photographicmaterial.

The results obtained are shown in Table-3. Sensitivities thereof areexpressed in the values relative to that of Sample No. 23 just aftercoated taking the value of 100.

It can be found the fact from Table-3 that a photographic materialhaving a high sensitivity and of which the preservability has greatlybeen improved can be obtained by combining the compounds of theinvention with an emulsion in which the reduction-sensitization wasprocessed inside the silver halide grains thereof, even if the compoundsof the invention were added in the protective layer of said photographicmaterial.

Also, there has been obtained the similar results from the sameexperiment as performed in this example, except that silver ripening wasreplaced by thiourea dioxide.

                  TABLE-3                                                         ______________________________________                                        Sam-                 Developed just                                                                            Developed af-                                ple  Compound added  after coated                                                                              ter heat-treated                             No.  (mg/mol of AgX) S      Fog  γ                                                                           S    Fog  γ                        ______________________________________                                        23   None                100  0.05 2.3 65   0.03 2.2                          24   Compound 17                                                                                200mg  98   0.04 2.3 94   0.04 2.3                          25      "       1,000mg  95   0.03 2.4 103  0.02 2.3                          26   Compound 39                                                                                200mg  97   0.04 2.3 94   0.04 2.3                          27      "       1,000mg  94   0.02 2.4 102  0.02 2.4                          28   Compound 53                                                                                200mg  99   0.04 2.3 95   0.04 2.3                          29      "       1,000mg  96   0.03 2.4 105  0.02 2.4                          ______________________________________                                    

EXAMPLE-4

Silver nitrate solution was added in the solution containing potasiumbromide, potassium iodide and gelatin, taking the period of 60 minutes.At the point of time passed for 20 minutes after the precipitation wascommenced, thiourea dioxide of 0.1 mg/mol of AgX was added further. Theemulsion thus obtained was silver iodobromide emulsion containing 6 mol%of silver iodide in form of a polydispersed octahedral twin having theaverage diameter of 0.9μ.

After desalted, gold-sensitization and sulfur-sensitization wereprocessed, and then 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene was added.

The emulsion thus obtained was devided by six portions and one of whichwas used for the control and five other portions were respectively addedwith the compounds indicated in Table-4. These six kinds of theemulsions were coated on and dried up respectively. At the time ofcoating, sensitizing dye [I],α-(1-benzyl-2,4-dioxy-3-imidazolidinyl)-α-pivalyl-2-chloro-5-[γ-(2,4-di-t-amylphenoxy)butylamide]acetanilideas to a yellow coupler and the popular additives for photographic usesuch as spreading, thickening and hardening agents were added, and thencoated and dried up in the conventional process so that the coatingratio can be at Ag 20 mg/100 cm² on a sublayered cellulose triacetatefilm base, and thus Sample No. 30-No. 37 were prepared respectively.

Sensitizing dye [I] ##STR29##

These samples were exposed to light through a blue wedge (for the periodof 1/50 second) and then color-developed, bleach-fixed, washed anddried-up, and thus a yellow image was obtained respectively from eachsample.

And, sensitometric tests were performed with each of both samples justafter coated and the samples heat-treated at 55° C. and 80% R.H. and for72 hours.

The results obtained are shown in Table-4. Sensitivities thereof areexpressed in the values relative to that of Sample No. 30 just aftercoated taking the value of 100.

It can be found the fact from Table-4 that a color photographic materialhaving a high sensitivity and of which the preservability has beengreatly improved can be obtained by containing the compounds of theinvention in emulsions reduced and sensitized inside the silver halidegrains thereof.

On the other hand, such effects as above cannot be obtained from anysample using any compound other than but similar to those of theinvention.

                                      TABLE-4                                     __________________________________________________________________________                          Developed just                                                                         Developed after                                Sample                                                                            Compound added    after coated                                                                           heat-treated                                   No. (mg/mol of AgX)   S  Fog                                                                              γ                                                                          S  Fog                                                                              γ                                  __________________________________________________________________________    30  None              100                                                                              0.04                                                                             0.65                                                                             70 0.03                                                                             0.62                                     31  Compound 57   100mg                                                                             98 0.04                                                                             0.65                                                                             90 0.03                                                                             0.63                                     32     "          200mg                                                                             95 0.03                                                                             0.68                                                                             94 0.02                                                                             0.68                                     33     "          500mg                                                                             90 0.02                                                                             0.73                                                                             98 0.02                                                                             0.73                                     34  Compound 62   100mg                                                                             99 0.04                                                                             0.65                                                                             90 0.03                                                                             0.62                                     35     "          500mg                                                                             93 0.02                                                                             0.75                                                                             98 0.02                                                                             0.74                                     36                                                                                 ##STR30##    100mg                                                                             95 0.04                                                                             0.67                                                                             68 0.03                                                                             0.63                                     37     "          500mg                                                                             85 0.03                                                                             0.70                                                                             63 0.02                                                                             0.67                                     __________________________________________________________________________

What is claimed is:
 1. A silver halide photographic emulsioncharacterized in that it comprises silver halide grainsreduction-sensitized in a process of growing the silver halide grains,and a compound represented by the following General Formula [I]:##STR31## (wherein R₁ and R₂ are selected from the group consisting of ahydrogen atom, an alkyl group, an alkenyl group, an aryl group, an acylgroup and a cycloalkyl group and R₃, R₄, R₅ and R₆ are selected from thegroup consisting of a hydrogen atom, a halogen atom, a hydroxy group, analkyl group, an alkenyl group, a cycloalkyl group, an aryl group, analkoxy group, an acyl group, a carboxyl group, an aldehyde group, anamino group, a sulfo group, an alkylthio group, an acylamino group, anaryloxy group, an arylthio group, an alkylamino group, an alkoxycabonylgroup and a sulfonamide group.)
 2. A silver halide photographic emulsionaccording to claim 1, the silver halide grains are reduction-sensitizedby adding a reducing agent and/or a water-soluble silver salt to theemulsion.
 3. A silver halide photographic emulsion according to claim 1,the silver halide grains are further sensitized by gold and/or sulfur.4. A silver halide photographic emulsion according to claim 3, thesensitization by gold and/or sulfur is carried out, after completion ofthe reduction-sensitization of the silver halide grains.
 5. A silverhalide photographic emulsion according to claim 2, the reducing agent isthiourea dioxide or stannous chloride.
 6. A silver halide photographicemulsion according to claim 2, the water-soluble silver salt is silvernitrate.
 7. A method for producing a silver halide photographic emulsioncomprising:(1) reduction-sensitizing in a process of growing the silverhalide grains and (2) adding a compound according to claim 1 to thesilver halide photographic emulsion.
 8. A method according to claim 7,reduction-sensitizing is carried out by adding a reducing agent and/or awater-soluble silver salt to the emulsion.
 9. A method according toclaim 8, the reducing agent is thiourea dioxide or stannous chloride.10. A method according to claim 8, the water-soluble silver salt issilver nitrate.
 11. A method according to claim 7, the silver halidegrains are further sensitized by gold and/or sulfur.
 12. A methodaccording to claim 11, the silver halide grains are further sensitizedby gold and/or sulfur after completion of the reduction-sensitization ofthe silver halide grains.
 13. A light-sensitive silver halidephotographic material comprising a support and a silver halidephotographic emulsion comprising silver halide grains,reduction-sensitized in a process of growing the silver halide grains,and a compound according to claim
 1. 14. A light-sensitive silver halidephotographic material according to claim 13, the silver halide grainsare reduction-sensitized by adding a reducing agent and/or awater-soluble silver salt to the emulsion.
 15. A light-sensitive silverhalide photographic material according to claim 13, the silver halidegrains are further sensitized by gold and/or sulfur.
 16. Alight-sensitive silver halide photographic material according to claim13, the silver-halide grains are further sensitized by gold and/orsulfur after completion of the reduction-sensitization of the silverhalide grains.
 17. A light-sensitive silver halide photographic materialaccording to claim 14, the reducing agent is thiourea dioxide orstannous chloride.
 18. A light-sensitive silver halide photographicmaterial according to claim 14, the water-soluble silver salt is silvernitrate.